Vehicular clutch assemblies are well-known devices for selectively disengaging an automatic or manual transmission from a vehicle's internal combustion engine during operation of the engine. One of the most common types of vehicular clutch assemblies includes a clutch disc, a pressure plate, a diaphragm spring (also referred to as a “plate spring”), and a thrust bearing (also referred to as a “throw-out bearing”). The clutch disc, pressure plate, and diaphragm spring are slidably mounted around the transmission input shaft and rotate in conjunction therewith. The thrust bearing is also slidably mounted around the transmission input shaft, but generally remains stationary as the input shaft rotates. The clutch assembly normally resides in an engaged position wherein the clutch disc frictionally engages a flywheel driven by the engine resulting in rotation of the clutch disc, pressure plate, diaphragm spring, and the transmission input shaft. To disengage the clutch assembly, the thrust bearing is pressed against the diaphragm spring, which urges the pressure plate and the clutch disc to move away from, and therefore frictionally disengage from, the engine-driven flywheel. When the clutch assembly is moved into the disengaged position, the rotation of the clutch disc, the pressure plate, the diaphragm spring, and the transmission input shaft is slowed or halted to facilitate transmission gear changes. In the case of a manual transmission, disengagement of the clutch assembly is typically controlled by a driver-actuated clutch pedal, which is mechanically linked to the thrust bearing by one or more intervening structures (e.g., a clutch lever and/or a hydraulic system).
The phrase “clutch pedal apply force” is commonly utilized to describe the force that a driver must apply to depress the clutch pedal. The clutch pedal apply force varies over the clutch pedal's range of travel and typically peaks near disengagement of the clutch assembly. For many drivers, such as those with arthritic knees, utilizing a clutch pedal that requires relatively high clutch pedal apply forces can be uncomfortable. Driver discomfort is especially problematic in high horsepower platforms wherein the peak apply force tends to be relatively high (e.g., approaching or exceeding approximately 130 Newton). A limited number of powered and unpowered pedal assist devices have been implemented in some vehicles (e.g., semi-trailer trucks) to lower the driver-required apply force over a portion or over the entirety of the clutch pedal's range of travel. However, in the case of powered pedal assist devices, such assist devices tend to be relatively complex, costly to implement, and often exhibit a noticeable lag between driver actuation of the clutch pedal and the generation of the assist force. Furthermore, in the case of certain proposed unpowered pedal assist devices, the assist device may bias the clutch pedal toward the depressed position over the pedal's initial range of travel, which may result in undesirable wear between clutch assembly components (e.g., the thrust bearing and the spinning diaphragm spring). Finally, in the case of both powered and conventional unpowered pedal assist devices, such devices are often incorporated directly into the clutch assembly (e.g., integrally formed as part of the clutch pedal lever) and are consequently impractical to retrofit to an existing clutch assembly.
There thus exists an ongoing need to provide embodiments of an unpowered pedal assist device for use in conjunction with a clutch assembly (or other vehicular control pedal assembly) that significantly reduces clutch pedal apply forces, that is relatively inexpensive to implement, that is reliable, and that exhibits substantially zero lag between driver actuation of the clutch pedal and generation of the assist force. It would be desirable if embodiments of such an unpowered pedal assist device were amenable to aftermarket installation on existing vehicles. It would further be desirable if such an assist device would initially bias the clutch pedal toward the non-depressed position to ensure that, after being depressed, the clutch pedal returns to the non-depressed or upright position to minimize wear between clutch assembly components. Finally, it would be desirable to provide embodiments of a clutch assembly including such an unpowered pedal assist device. Other desirable features and characteristics of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying Drawings and this Background.